Third party funded individual grant
Start date : 01.04.2020
End date : 30.09.2024
Extension date: 31.03.2026
Steel fibers applied in reinforced concrete contribute to the high strength and versatility of the composite. Conventionally produced by wire drawing, they show variations in their geometrical and mechanical properties. For a technologically and economically more efficient manufacturing, an alternative production procedure consisting of notch rolling and cyclic bending has been developed. At first a wire strip is created from a strip material by pressure forming. The following process step – cyclic bending – initiates predetermined breaking points on the formed webs through material fatigue. When finally breaking, they exhibit a smooth and burr-free parting surface. The resulting advantages are the easy-to-handle starting material, leading to a shortening of the process time with simultaneous homogeneity of the geometrical and mechanical properties. For directly adjusting these properties of the semi-finished products, a holistic understanding of the manufacturing procedure is required. Due to insufficient material-specific knowledge about the hardening and damage behavior, an evaluation of relevant process parameters is hardly possible so far.
The aim of this research project is a fundamental experimental and numerical analysis of the process chain of notch rolling and cyclic bending for the production of steel fibers. The holistic examination enables a determination of process influencing variables and interactions that are to be correlated with the process limits with regard to a process window. The mapping of the relevant characteristics of behavior for the numerical analysis base on selected material and damage models and experimentally determined characteristic values. The resulting simulation models of the two process steps are validated by analyzing the material flow and the process characteristics of the experimental implementation of the sub-processes. With the help of these models, a comparative evaluation of the effects of changes in process parameters is possible. Finally, the experimental and numerical combination of the process steps and their investigations enables an analysis of the process parameters and their interactions in the overall process.
In order to increase the productivity of the production process of steel wires, the process chain of notch rolling and cyclic bending is fundamentally analyzed. During notch rolling, notches are formed on both sides of a sheet metal strip, in whose areas the material fatigues and forms cracks during the subsequent fulling process. The numerical and experimental implementation of both process steps enables the identification of relevant influencing parameters and their interactions. Parameters taken into account are, among others, the notch radius, notch angle and web thickness in notch rolling, and the bending angle and number of cycles to breakage or to the desired residual web thickness in cyclic bending. Numerical and experimental studies of ductile damage are required to evaluate material separation.